Bolt detent for a firearm



Aug. 23, 1955 B. DARslE 2,715,857

BOLT DETENT FOR A FIREARM HTTOENEYS Aug. 23, 1955 B, DARSiE 2,715,857

BOLT DETENT FOR A FIREARM Filed Jan. 19, 1953 2 Sheets-Sheet 2 Q Q vr m WIW 86 -HHH 1N VEN TOR.

l P :El-urns :Un-rsia 5f. BY

Unite BOLT DETENT F R A FIREARM Application January 19, 1953, Serial No. 332,133

6 claims. (c1. 89-181) This invention relates to automatic firearms and particularly to the class in which the bolt is known as the free bolt type.

In firearms using the free bolt it is not necessary to employ driving springs to return the bolt to the battery position thereby allowing the use of a shorter bolt and resulting in a shorter rearm which is an essential factor in present day firearm design.

Firearms of the aforesaid type, wherein the bolt is returned to the battery position through the resulting medium of the impact force on the buler mechanism thereby generating forward movement to the bolt, require a positive locking means to prevent the rebounding of the bolt out of the locked battery position.

ln prior art firearms of the above type, the locking means comprising a spring-biased latch necessitated the use of a very heavy spring to secure the bolt in the battery position that naturally reduces the cyclic rate of the rearm by increasing the load that the bolt has to overcome to move the bolt into the battery position.

A particular object of this invention is to provide a simple but effective resilient means for holding the bolt in the battery position.

Another object of this invention is to provide resilient means suiciently strong to secure the bolt in the battery position and still permit the manual charging of the bolt when the bolt -is in the battery or between a battery and recoil position.

A further object of this invention is the provision of an improved bolt latching means adapted to be released in one direction by a much lesser amount of force than lthat required to effect a release thereof in the opposite direction. t

Another object of this invention is to provide a double action latching means for releasably holding a firearm bolt in battery position whereby a minimum amount of force has to be overcome when the bolt is going into the battery position but a greater amount of force has to be overcome to effect disengagement of the latch during recoil of the bolt.

Another object of this invention is to provide double action latching means for releasably holding a firearm bolt in battery position whereby the latch engages during a very short travel of the bolt when the bolt is vgoing into the battery position but requires a much longer travel of the bolt to effect disengagement of the latch.

Still another object of this invention is to provide bolt latching means for a firearm utilizing a charger on both sides thereof.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

Fig. 1 shows a longitudinal cross-section of a rearm using the present invention showing the bolt in the recoil position;

Fig. 2 shows an enlarged cross-sectional side View of the bolt assembly in relation to the charger lugs;

t States Fatent Fig. 3 is a view similar to Fig. 1 with the bolt in the battery position;

Fig. 4 is a bottom perspective view of the bolt showing the latches therein;

Fig. 5 is a perspective view of the lever; and

Fig. 6 is a perspective view of the latch.

Referring to Fig. 1 of the drawings, reference numerals 12, 14 and 16 designate the receiver, buffer, and breech mechanism, respectively, of a large caliber, high speed, electrically fired automatic machine gun. Reference nurnber 18 designates a bolt assembly that is slidably mounted in receiver 12 between a battery and recoil position and that does not require the use of driving springs to return the bolt to the battery position depending instead upon the impact force on the buffer mechanism whereby said assembly is returned to the battery position.

Bolt assembly 18 comprises a bolt body 20 and a bolt head 22 mounted therein for partial rotation relative to the bolt body 20. Bolt head 22 is provided with interrupted ring segments 34 which are adapted to interlock with complementary interlocking ring segments 36 provided within breech mechanism 16 upon approximately /7 of a turn of bolt head 22. Rearwardly of and aligned with ring segments 34 of bolt head 22 there is provided a pair of studs 38 oppositely disposed and arranged for mounting a pair of rollers 40 to cooperate with a cam surface 42 located on the rear of breech mechanism 16.

On each side of bolt body 20, a slot 46 is located in the forward end thereof to receive an inertia block or cam 48 slidably mounted therein and biased forwardly by a spring 50. Cam 48 comprises a front cam nose portion 52 for cooperation with rollers 4l) when bolt body 20 moves forwardly into the battery position thereby locking said head in the battery position through the interlocking of ring segments 34 with 36. Bolt body 20 is provided on the left side with an electrical contact 162 at the rear end thereof arranged to energize a tiring pin (not shown) when contact 102 engages Contact 11294 mounted on the left side of receiver 12.

Bolt body 20, on the extreme rear end, is provided with a pair of downwardly depending charger lugs 54 from the bottom thereof spaced an equal distance apart from the longitudinal center line of such bolt body. Bolt body 20, forwardly of lugs S4, is provided with a pair of slots or recesses 56 an equal distance apart and longitudinally aligned with charger lugs S4. Slots 56 comprise a rear vertical wall 58 extending from the bottom to the top of bolt body 20 and a forwardly disposed vertical wall 60 extending from the bottom and terminating in a rearwardly and upwardly disposed angular sur ace 62 whereby slots 56 have a smaller opening in the top of bolt body 20 than the opening in the bottom surface thereof. Angular surface 62 is provided with a stud 64 to receive a compression spring 65.

Bolt body 20 is provided with a transverse hole 68 therethrough that passes through the upper rear portion of slots 56. FiXedly mounted in hole 68 is a shaft '79 arranged to receive a lever 72 rotatably mounted thereon in each of said slots 56. Lever 72 is provided with a bifurcated end 74 having a shelf portion 76 therein constructed to act as a stop for a latch 78 when a lug thereon contacts such shelf portion. Latch 78 is pivotally mounted to lever 72 in the lower front end of bifurcated portion 74 by a pin 80. Latch 78 is provided with an angular surface 82 parallel to angular surface 62 of slots 56. Angular surface 82 is provided with a stud 84 similar to stud 64 arranged to receive the opposite end of compression spring 66 whereby lever 72 and latch 78 are biased as a unit in a clockwise direction. Lever 72 is provided with a vertical rear surface 98 whereby such surface limits the clockwise rotation of lever 72 when said surface contacts wall 58 3 of slots 56. Latch 78 is provided with a toe portion 86 that protrudes downwardly through the bottom of slots 56 of bolt body 20 for cooperation with a charger nut 88 of a charger assembly 90.

A charger assembly 9i) is longitudinally mounted on each inside vertical surface of receiver 12 oppositely opposed to each other and directly below bolt ways 186 whereon the bolt assembly 18 moves along between a battery and recoil position. Each charger assembly 90 is provided with a double-acting screw mechanism 108 that is actuated by an air-propelled piston 110. Screw mechanism 188 comprises an inner screw 112 fixedly secured to the front end of screw mechanism 108 and an outer screw 114 being of tubular configuration having internal and external threads. internal threads of outer screw 114 cooperate with the inner screw 112 and the external threads thereon cooperate with internal threads (not shown) provided in charger nut 88. Charger nut 88 is provided with an upstanding lug 116 with a vertical surface 118 on the front end thereof for cooperation with latch 78 and a vertical surface 126 on the rear end thereof for cooperation with charger lug 54 of bolt body 26. More detailed description of charger assembly 90 is recited in my copending application, Serial No. 334,764, filed February 2, 1953, for Charging Devices for a Firearm.

Buffer mechanism 14 is vertically mounted and centrally located in the rear end of receiver 12 to absorb the recoil impact of bolt assembly 18 in the conventional manner and comprises an upper and lower buffer unit 92 connected by a substantially vertically disposed buffer bar 94. Buffer unit 92 is provided with a stack of resilient washers 96 to absorb the recoil impacts.

Operations Surface 120 of nut 88, when positioned in the battery position cams latch 78 in a clockwise direction directly against the bias of spring 66 during the counter-recoil movement of bolt assembly 18 when such latch therein moves forwardly over lug 116. After latch 78 passes over lug 116, it resumes its normally extended position being biased downwardly in a counterclockwise direction through the medium of spring 66. Toe 86 of latch 78 is then directly in front of vertical surface 118 of charger nut 88. Latch 78 then holds bolt assembly 18 more resiliently and effectively in the battery position through the increased spring pressure gained by the increase in the lever arm created when lug 100 of latch 78 contacts shelf 76 of lever 72.

Therefore, during the recoil movement of bolt assembly 18, when the latch 78 and lever 72 are acting as a unit, the work load that has to be overcome is multiplied due to the increased spring pressure and the longer engagement of latch 78 with lug 116 thereby retarding the initial movement of the recoil cycle of the bolt assembly resulting in a smoother recoil action. It will be noted in Fig. 2 that the lug 116 of charger nut 88 in the battery position is positioned between latch 78 and lug 54 and when it is necessary to manually charge the firearm, the lug 116 is moved rearwardly and engages lug 54 of bolt body 20 thereby carrying the bolt assembly 18 rearwardly to the recoil position.

When the firearm is being functioned in the conventional manner by normal explosions of fired rounds, the charger nut 88 is in the battery position at all times and when the bolt assembly 18 is returned to the battery position during counter-recoil, the latch 78 operates as aforementioned. When the bolt is in an intermediate position, that is, between the battery and recoil position, charging of the firearm is obtained by functioning the charger nut 88 rearwardly and when such nut strikes latch 78, the bolt assembly 18 will be moved rearwardly until such time that the rear end of the bolt body 20 strikes the buffer bar 94. Charger nut 88 will then depress latch 78 and such nut will continue rearwardly until the end of the complete stroke of the charger assembly 98 where- CII by lug 116 will be positioned between lug 54 of bolt body 20 and the toe 86 of latch 78 thereby holding the bolt assembly 18 in the recoil position. When the bolt assembly 18 is returned manually to the battery position by the charger assembly, the surface 118 of lug 116 contacts toe 86 of latch 78 thereby moving the bolt assembly to the battery position.

While spring 66 must have sufficient strength to hold latch 78 and lever 72 stationary against the rebounding force imparted to bolt body 20 upon conclusion of movement into battery, such strength, however, should not be great enough to prevent pivoting of latch 78 together with lever 72 out from in front of charger lug 116 as bolt body 20 recoils in response to the firing of a cartridge. In addition, the force required to pivot lever 72 together with latch 78 must not be greater than the force which keeps charger nut 88 in the battery position, otherwise the recoil movement of bolt body 20 would also operate charger assembly 90. At the same time, however, spring 66 must act on lever 72 through the medium of latch 78 with sufficient force to prevent any pivotal movement thereof while charger nut 88 is moving bolt body 20 forwardly into battery position. If this were not so, the inertia mass and frictional resistance of bolt body 2) could very well retard the forward movement thereof to such extent that latch 78 and lever 72 would be pivoted out of the path of forward movement of charger nut 83 and thereby permit such nut to override latch 78 and prevent bolt body 20 from moving into a fully locked battery position. In other words, spring 66 must be weak enough to effect yielding of the double acting latch of the present invention not only when the reaward charging movement of bolt body 20 is halted upon contact with buler bar 94 but during the recoil and counterrecoil firing movements of bolt body 20 as well, while at the same time spring 66 must be strong enough to prevent yielding of the latch during the rearward and forward charging movements of bolt body 20.

From the foregoing, it will be apparent to one skilled in the art that herein is disclosed a double action latching means that will secure a bolt in the battery position and also permit the manual charging of the bolt with a lesser amount of resistance.

While the form of embodiment of the invention herein disclosed constitutes a preferred form, it is understood that other forms might be adopted as may come within the scope of the claims which follow.

I claim:

1. In an automatic firearm having a receiver and a bolt slidably mounted therein for reciprocal movement between a battery and a recoil position, a lever mounted for pivotal movement within the bolt, a latch pivotally secured to the free end of said lever, spring means biasing said latch into engagement with said lever, stop means in the bolt for limiting the pivotal movement imparted to said lever by said latch and thereby limiting the extent to which said latch projects from the bolt, and fixed means abutting the rear end of said latch during battery position of the bolt, said spring means biasing said latch to coact with said fixed means and said lever for resisting the pivotal force imparted thereto by the tendency of the bolt to bounce out of battery position.

2. In an automatic firearm having a bolt slidably mounted therein for reciprocal movement between a battery and a recoil position, and a charger adapted to reciprocate the bolt independently of firearm operation, a lever mounted for pivotal movement within the bolt, a latch pivotally secured to the free end of said lever, spring means intermediate a fixed portion of the bolt and said latch for imparting pivotal movement thereto, means on said lever for limiting the relative pivotal movement imparted to said latch by said spring means, and stop means in the bolt for limiting the pivotal movement imparted to said lever by said latch and thereby limiting the extent to which said latch projects from the bolt, said latch being thereby positioned in contact with the front end of the charger when the bolt is in battery position and adapted to coact with said lever and with the charger in response to said spring means to resist the pivotal thrust imparted thereto by the bounce of the bolt out of battery position.

3. In an automatic firearm having a bolt slidably mounted therein for reciprocal movement between a battery and a recoil position, and a charger for reciprocating the bolt independently of rearm operation, the improvement of a double acting latch for resisting the rearward bounce of the bolt out of battery position comprising a lever portion mounted for pivotal movement within the bolt, a latching portion pivotally secured to the free end of said lever portion, spring means biasing said latching portion into engagement with said lever portion, said lever portion and said latching portion being mutually engageable for limiting the relative movement produced therebetween in response to said spring means, and stop means in the bolt for limiting the pivotal movement imparted to said lever portion by said latching portion under the bias of said spring means and thereby limiting the extent to which said latching portion projects from the bolt in front of the charger when the bolt is in battery position, said latching portion being adapted to simultaneously coact with said lever portion and the charger for preventing the bolt from bounching out of battery position but being also adapted to yield in response to the recoil thrust of the bolt and thereby override the charger.

4. In an automatic iirearm having a bolt slidably mounted therein for reciprocal movement between a battery and a recoil position, and a charger having an upwardly projecting lug engageable with the bolt for effecting reciprocal movement thereof independently of firearm operation, a lever mounted for pivotal movement within the bolt, a latch pivotally secured to the free end of said lever, projecting lug means on said lever and on said latch adapted to interengage upon pivotal movement of said latch outwardly of the bolt, spring means biasing said latch in a lever-engaging direction, and stop means in the bolt for limiting the pivotal movement imparted to said lever by said latch and thereby limiting the projection of the rear end thereof from the bolt, said projecting rear end portion of said latch being positioned in contact with the forward face of the charger lug when the bolt is in battery position whereby said latch coacts with said lever and with the charger lug under the urging of said spring means to block the rearward bounce imparted to the bolt upon movement thereof into battery position, said spring means being arranged to exert a lesser force on said coacting lever and latch than the force required to retract the charger whereby said latch pivots said lever away from said stop means in the bolt to override the charger lug upon recoil movement of the bolt.

5. In an automatic rearm having a bolt slidably mounted therein for reciprocal movement between a battery and a recoil position, the combination of a charger having an upwardly projecting lug engageable with the underside of the bolt whereby actuation of the charger reciprocates the bolt independently of iirearm operation, the bolt having a vertical recess therein, a lever pivotally mounted at one end thereof in said recess and having a bifurcated portion, a latch pivotally mounted to the opposite end of said lever between the sides of said bifurcated portion, said lever having a lug extending forwardly into said bifurcated portion to lie in the path of movement of said latch, said latch having a lug extending rearwardly therefrom for engagement with said lever lug, spring means pivoting said latch outwardly of said recess in the bolt to eiect engagement of said lug thereon with said lug on said lever whereby the corresponding pivotal movement of said lever is limited by the rear wall surface of said recess in the bolt, thereby limiting the extent to which the rear end of said latch projects from said recess in front of the lug on the charger, the strength of said spring means being sufficient to overcome the pivotal force imparted to said lever through said latch by the rearward bounce of the bolt normally resulting from the movement thereof into battery position but being insufficient to resist the pivotal movement imparted to said lever by the overriding travel of said latch past the lug on the charger.

6. In an automatic firearm having a bolt slidably mounted therein for unopposed reciprocal movement between a battery and a recoil position, and a pair of chargers each having an upwardly projecting lug on the front end thereof for reciprocating the bolt independently of rearm operation, the improvement of a double acting latch operable against each charger for resisting the rearward bounce of the bolt out of battery position, each latch comprising a bifurcated lever portion mounted for pivotal movement in the bolt, a latching portion pivotally secured to the free end of said bifurcated lever portion for movement relative thereto, interengaging lug means on said latching portion and on said lever portion, spring means biasing said latching portion to integrally coact with said lever portion and project downwardly from the bolt, and stop means in the bolt for limiting the pivotal movement imparted to the double acting latch by said spring means and thereby positioning said latching portion with the rear end thereof in front of the lug on each charger, the strength of each of said spring means being suicient to overcome the pivotal force imparted to said lever portion through said latching portion by the rearward bounce of the bolt normally resulting from the movement thereof into battery position but being insuicient to resist the pivotal movement imparted to said lever portion during overriding of the lug on the charger, the strength of each of said spring means being also suflicient to prevent the charger lug from overriding said latching portion during the rearward and forward charging movements of the bolt but being insufficient to prevent the charger lug from overriding said latching portion at the conclusion of the rearward charging movement of the bolt.

References Cited in the tile of this patent UNlTED STATES PATENTS 870,719 Freeman Nov. 12, 1907 1,926,816 Podrabsky Sept. 12, 1933 2,016,646 Mancini Oct. 8, 1935 2,100,097 Beharrel et al. Nov. 23, 1937 2,329,925 Mejean Sept. 21, 1943 2,389,996 Pontius Nov. 27, 1945 FOREIGN PATENTS 617,060 Germany Aug. 12, 1935 65,213 Denmark Dec. 9, 1946 131,773 Australia Mar. 15, 1949 

